from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from rapid.rapidforms import RapidAlternativesField
from django.db import models

__author__ = 'marcos'

"""
Model fields specific for Rapid Django.
"""


class AlternativeData(GenericForeignKey):
    """
    A generic relation that Rapid will display as an inline form or a group of data at the
     edit and view actions.

    Create like a Django GenericForeignKey, but use an AlternativeDataTables instead of a
    ForeignKey to ContentTypes.
    """
    def formfield(self, **kwargs):
        kwargs['form_class'] = RapidAlternativesField
        return super(GenericForeignKey, self).formfield(**kwargs)


class AlternativeDataTables(models.ForeignKey):
    """
    Use an AlternativeDataTables model field on AlternativeData represetntations, instead of
    a ForeignKey with ContentTypes.
    """
    def __init__(self, alternatives=[], **kwargs):
        """
        Receives the same named parameters of a ForeignKey, but instead of a target table,
        receives a list of the tables that may keep the alternative data.
        :param alternatives: List of the tables that hold the alternative data.
        :param kwargs: Arguments to the ForeignKey, without a relationship target.
        """
        pks=[]
        try:
            pks = [ContentType.objects.get_for_model(a).pk for a in alternatives]
        except RuntimeError:
            #Querying ContentType within a content type is an issue at migrations
            pass
        kwargs['limit_choices_to'] = {'pk__in': pks}
        kwargs['to'] = ContentType
        super(AlternativeDataTables, self).__init__(**kwargs)
        self.alternatives = alternatives